This invention relates to a V-belt transmission apparatus used for a stepless variable change speed machine for a vehicle or the like. More particularly, the invention is directed to a V-belt transmission apparatus having a large number of V-shaped metallic members disposed in series in stacked condition along on a metallic belt means forming, as a whole, a V-belt assembly, with this assembly being arranged around a driving pulley and a driven pulley so as to enable power transmission between the two pulleys.
A known apparatus of this kind is disclosed in Japanese Patent Application Publication No. Sho 57-58543 and is shown in FIG. 1. Two metallic belts a, a constituting the belt means are disposed laterally in parallel one with another. Each V-shaped member b is provided with laterally open channel-shaped grooves c, c made on both sides thereof. The metallic belt a on each side is inserted in the channel-shaped groove c on each side. It has been usual with such an apparatus that the groove c on each side is formed, by means of blanking or the like, and is defined by a grooved wall surface in an integral part of the metallic member b as shown in FIG. 1.
When the V-shaped metallic member b is engaged with the V-pulley d during an operation, a lower wall surface c.sub.1 in each channel-shaped groove c of the V-shaped metallic member b is in strong pressure contact with an inner facing surface of each metallic belt a. When the metallic member b is disengaged from the V-pulley d, the lower wall surface c.sub.1 or an upper wall surface c.sub.2 in each groove c of the V-shaped metallic member b is in contact with the inner facing surface or an outer facing surface of each metallic belt a. Accordingly, in order to prolong the service life of the belt, it is desirable that these wall surfaces c.sub.1, c.sub.2 be smoothly finished. It is additionally desirable that the lower wall surface c.sub.1 be a curved surface corresponding to a curve of the metallic belt a caused by the engagement thereof with the V-pulley d. Because the channel-shaped groove c is formed in the integral part of the V-shaped metallic member b, the resultant shape of the sidewardly open channel-shaped groove c is narrow in a vertically width thereof (as shown in FIG. 1) and is deep in the depth thereof. Such a construction results in a problem that the finishing work on the wall surfaces c.sub.1, c.sub.2 is very difficult.